1. Field of the Invention
The present invention relates to a recording apparatus configured to discharge ink droplets of different volumes and to record dots of different diameters on a recording medium.
2. Description of the Related Art
An inkjet recording apparatus records an image by discharging ink droplets of various colors from a plurality of ink discharge ports arranged on a recording head. Conventionally, an inkjet recording apparatus which forms dots of different diameters on a recording medium by discharging ink droplets of different volumes is known. For example, Japanese Patent Application Laid-Open No. 8-11298 discusses a method of forming small dots having small diameters at a higher resolution than large dots having large diameters on a recording medium.
FIG. 1B is a diagram showing the layout pattern of dots on one pixel for each gradation value. FIG. 1B shows an example of a dot layout on one pixel for representing each gradation value when large dots 100 and small dots 101 are formed. The horizontal axis corresponds to each gradation value, and the gradation value becomes higher from the left to the right. The layout of dots on one pixel is illustrated above the horizontal axis indicating each gradation value. FIG. 1B shows a dot layout in the case where small dots 101 are formed at a higher resolution as compared to large dots 100, as discussed in Japanese Patent Application Laid-Open No. 8-11298.
In such a dot layout pattern corresponding to each gradation value, a pixel is filled with large dots when the gradation value is highest. Consequently, a high recording density can be realized. Moreover, a large number of gradation levels can be represented in the intermediate region such that an image free of granular quality can be obtained.
However, in an inkjet recording apparatus, an air current generated along the discharged ink droplet causes displacement of the impact position of the ink droplet. Such displacement can lead to the degradation of image quality. In particular, when a high-resolution recording is performed, the number of ink discharges per unit time increases such that a large air current is generated. Consequently, the degradation of image quality increases due to the effect of the air current. Additionally, small ink droplets have less weight as compared to large ink droplets and are more prone to the effect of air current.
Therefore, when small dots are formed at a high resolution as discussed in Japanese Patent Application Laid-Open No. 8-11298, the position where the dot is formed is easily displaced due to the effect of air current, thus leading to the degradation of image quality.